Figure 1.
Spectral analyses of full-night snoring sounds including power spectra of overall snore events (A–D) and energy spectrum of an overnight snore map (E–H).
(A) & (E) Primarily monosyllabical low-frequency snoring (type 1 snore map). (B) & (F) Duplex low- and mid-frequency snores (type 2). (C) & (G) Duplex low- and high-frequency snoring (type 3). (D) & (H) Triplex low-, mid-, and high-frequency snores (type 4).
Table 1.
Demographic characteristics, snoring questionnaires, polysomnographic parameters, and snore map type.
Figure 2.
The spectrum of snoring sound (red line) and background noise (black line).
Note that the duration of snoring sound was between 0.6 and 4.0 seconds (blue box) and noise intensity in sound pressure level was general less than 10 dB when frequencies were higher than 450 Hz (green box).
Figure 3.
An example of an energy spectrum construction.
(A) Sound intensities of the nine detected snores after an apnea event within one minute. (B) Three dimensional figure showing the power spectrum of each snoring episode. (C) Two dimensional figure showing nine power spectra together. (D) Energy spectrum strengthening the contributions of the predominately loud snoring sounds and helping us to type the snore map.
Figure 4.
Energy spectrum of the 20 subjects categorized by energy typing showing their exact distributions of snoring sound energy.
Some cases with low amplitude of snoring sound energy needed adjustment of the Y-axis scales for an easier typing.
Table 2.
Demographic characteristics, snoring questionnaires, and polysomnographic parameters among four snore map types.
Table 3.
Snoring power spectral data among four snore map types.
Figure 5.
Scatter plots of clinical parameters versus snore map type.
(A) A scatter plot of body mass index (BMI) versus snore map type. (B) A scatter plot of neck circumference versus snore map type. (C) A scatter plot of apnea-hypopnea index versus snore map type. (D) A scatter plot of severity of obstructive sleep apnea syndrome (OSAS) versus groups of snore map type. After adjustment for BMI and neck circumference, snore map type 3–4 was significantly associated with severity of OSAS (R2 = 0.28, P = 0.026). Blue dashed line indicates linear fit line.
Table 4.
Comparison of demographic characteristics, snoring questionnaires, polysomnographic parameters, and acoustic parameters between the snore map type 1–2 group and the snore map 3–4 group.